Malfunction detector for detecting open-circuit condition at DC generator output terminal

Abstract

A malfunction detector for detecting an open-circuit condition at the output terminal of a vehicular DC generator is disclosed. The frequency of a signal derived from one of the armature windings of the generator, for instance, at an end or neutral terminal, is compared with the control frequency of the voltage regulator, which may be derived from a field winding of the generator. If the latter is equal to the former, an indication of an open-circuit condition is given.

I claim: 
     
       1. A malfunction detecting device for detecting an open-circuit state at an output circuit of a vehicle-mounted DC generator driven by an engine of a vehicle and including a voltage regulator, comprising: means for comparing a frequency of a signal derived from an armature winding of said DC generator and a control frequency of said voltage regulator, and indicating means responsive to an output of said comparing means for indicating a malfunction when said control frequency is equal to or greater than said frequency of said signal derived from said armature winding. 
     
     
       2. The malfunction indicating device as claimed in claim 1, wherein said signal derived from said armature winding is a voltage between an end point of a predetermined armature winding of said DC generator and a ground terminal of said DC generator. 
     
     
       3. The malfunction indicating device as claimed in claim 1, wherein said signal derived from said armature winding is a voltage between a neutral point of said armature winding and a ground terminal of said DC generator. 
     
     
       4. The malfunction indicating device as claimed in claim 1, wherein said comparing means comprises first and second frequency detectors having inputs coupled to said armature winding and a field winding, respectively, of said DC generator, and a microcomputer receiving outputs from said second frequency detectors.